1. Field of the Invention
The present invention relates to an electric hoist
2. Description of the Related Art
In an electric hoist, preferably the lifting speed and the lowering speed of the hoist can be made lower when a load is lifted by the hoist, to thereby prevent an impact of the load with a surrounding member such as a floor, at a high speed, and the lifting speed and the lowering speed of the hoist can be increased under a no-load state, to thereby quickly lift or lower the hook of the hoist to a target position.
In a known electric hoist, the upper end of the wire rope for lifting a load is supported by a spring-loaded movable member, and a detecting switch cooperating with the spring-loaded movable member is provided for detecting whether or not there is a load on the hook of the wire rope. When it is detected by the detecting switch that there is a load on the hook, the lifting speed and the lowering speed of the hoist are made lower, and when it is detected by the detecting switch that there is no load on the hook, the lifting speed and the lowering speed of the hoist are increased (see Japanese Unexamined Patent Publication No. 57-38294).
This type of electric hoist, however, requires additional special members, such as the spring-loaded movable member, to detect whether or not there is a load on the hook, and thus a problem arises in that the size of the hoist becomes large, and the cost of manufacturing the hoist is increased.